Piston grinding machine



H. A. SILVEN 2,213,030

3 Sheets-Sheet 1 Filed May 3. 1959 PISTON GRINDING MACHINE Aug. 27, 1940.

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Aug. 27, 1940. H. A. SILVEN 2,213,030

PISTON GRINDING MACHINE Filed May 3, 1939 3 Sheets-Sheet 2 HERBERT A. ILVEN Aug. 27, 1940. H. A. SILVEN PISTON GRINDING MACHINE Filed May 3, 1939 3 Sheets-Sheet 5 Emmi R mE MN wk m3 MW HERBERT A. 51L VEN Patented Aug. 27, 1940 FFHCE PESTQN GRINDING MACHINE tion of Massachusetts Application May 3, 1939, Serial No. 271,451

9 Claims.

The invention relates to grinding machines, and more particularly to an apparatus for grinding a work piece of a non-circular cross-section, such an oval shape on an automotive piston.

One object of the invention is to provide a simple and thoroughly practical grinding apparatus for grinding a work piece to a non-circular shape. Another object of the invention is to provide a grinding apparatus for grinding a work piece of non-circular cross section, in which the work piece is oscillated toward and from the grinding wheel by means of a rotatable cam. A further object of the invention is to provide a piston grinding attachment for grinding an oven or elliptical surface on the periphery of a work piece, such as a piston. Another object is to provide a readily interchangeable master cam which is mounted on the end of the headstock spindle adjacent to the grinding wheel. A further object is to provide a Work supporting and driving element which is adjustably mounted on the master cam.

A further object of the invention is to provide a piston grinding attachment in which the piston being ground is moved longitudinally from a grinding position to a truing position and vice versa before and after a truing operation. A further object of the invention is to provide such a piston grinding apparatus with an automatically actuated mechanism for shifting the piston support to and from an operative position before and after a grinding wheel truing operation as the piston is moved to and from its loading and grinding position. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is shown one of various possible embodiments of the mechanical features of the invention,

Fig. l is a front elevation of the improved piston grinding apparatus;

Fig. 2 is a fragmentary cross sectional view, on an enlarged scale, taken approximately on the line 22 of Fig. 1;

Fig. 3 is a fragmentary longitudinal sectional view taken approximately on the line 3-3 of Fig. 2;

Fig. i is a fragmentary sectional view, on an enlarged scale, taken approximately on the line ll of Fi 2.;

(Cl. 51-l01) Fig. 5 is a fragmentary cross sectional view, on an enlarged scale, taken approximately on the line 55 of Fig. 1;

Fig. 6 is a fragmentary front View, on an enlarged scale, of the lever and cam mechanism for 5 moving the rock bar to and from an operative position;

Fig. '7 is a fragmentary cross sectional view taken approximately on the line l-'l of Fig. 3; and

Fig. 8 is a fragmentary horizontal sectional View, taken approximately on the line 88 of Fig. 6, through the toggle lever mechanism for rocking the rock bar to and from an operative position.

A cylindrical grinding machine has been illustrated in the drawings comprising a base If] which supports a longitudinally traversable work supporting table H on the usual flat way I2 and v-way It. The work supporting table II is ar- 20 ranged to be traversed longitudinally relative to the base iii to traverse a work piece and position it in operative relation with a rotatable grinding wheel to. The table l I is provided with a depending rack bar l6 by which the table may be 25 traversed by a manual or power operated traversing mechanism. For the sake of illustration,

a manually operable traverse mechanism has been illustrated which is identical with that shown in the prior U. S. Patent to C. H. Norton, N0. 30 1,299,765, dated April 8, 1919, to which reference may be had for details of disclosure not contained herein. A gear I l meshes with the rack bar It and is rotatably supported on a shaft 3. The shaft l8 also supports a gear I9 35 which is either formed integral with or fixedly mounted relative to the .gear ll. The gear l9 meshes with a pinion 2ll which may be rotated by means of the manually operable hand traverse wheel 2 l By rotation of the hand traverse wheel 2! in either direction, a traversing movement of the table ll may be obtained.

The rotatable grinding wheel I5 is supported on a wheel spindle (not shown) which in turn is rotatably journalled in a transversely movable wheel slide 26. The wheel slide 26 is supported on a transversely extending V-Way 21 and a flat way 28 formed on the base II]. The grinding wheel l5 and its supporting spindle may be driven by any suitable driving mechanism such as, for example, an electric motor 29 which is mounted on the upper surface of the wheel slide 26. The motor is provided with a rotatable armature shaft 39 which is provided with a driving pulley 3!. The pulley 3| is connected by multiple V-belts 32 with a pulley 33 mounted on the outer end of the wheel spindle.

The wheel slide 26 is arranged to be fed transversely toward and from the work supporting table ii to facilitate feedin of the grinding wheel l5 toward and from the work axis to grind a work piece to the required extent. The feeding mechanism illustrated in the drawings is substantially the same as that shown in the prior United States patent to C. H. Norton No. 762,838 dated June I l, 1994, to which reference may be had for details of disclosure not contained herein. A half nut 35 depending from the wheel slide 26 meshes with or engages a rotatable cross feed screw 38. A forwardly extending portion 3'! of the feed screw carries a gear which in turn meshes with a pinion 39. A manually operable feed wheel lll is either formed integral with or fixedly mounted to the gear so that rotation of the manually operable feed wheel ll] is transmitted through the gear the gear 38, the shaft feed screw 36 to cause a transverse feeding movem nt of the half nut 35, the wheel slide the grinding wheel l5. A pivotally iounted feeding stop is provided which is arranged to engage an adjustably positioned abutment (not shown) carried by a micrometer adjusting mechanism to facilitate fine adjustment of the feeding mechanism so as to compensate for wheel wear. ien the fee wheel 55 is rotated in a counterclockwise direction, an infeeding movement of the grinding wheel i5 is obtained, and arly wl'len the feed wheel to is rotated in the reverse direction, a rearward movement of the grinding wheel is obtained.

The table l 5 serves as a support for a rotatable work supporting mechanism. A pair of spaced members 1-5 and C6 are mounted on the upper surface of the swivel table These members 45 and it are provided with journal bearings ll and which serve as a support for the reduced end portions and 5?] of a cylindrical bar 5!. The bar 5i serves as a rotatable support for a rock bar 52. In order that the rock bar 52 may rock freely relative to the shaft 55, anti-friction bearings 53 and 54 are interposed between the ends of the rock bar and the shaft 5i. A headstock 58 and a footstock 59 are formed integral with the rock bar The headstock 58 supports a rotatable headstock spindle 653 in bearings 65 and The left-hand end of the headstock spindle (Fig. 3) is provided with a driving pulley which i connec ed by a multiple V-belt drive 6 5 with a multi-grooved pulley G5 which is keyed to the rotatable shaft 56. The shaft to is supported by anti-friction bearings l5? and G8 which are in turn supported within an eccentric sleeve 69 which is adjustably mounted in a bearing portion i l formed in the upper end of a bracket '5 i which is fixedly mounted relative to the base member 65. The left-hand end of the shaft 65 is provided with a multi-grooved pulley 72 which is connected by a multiple V-belt drive 73 with a pulley i l which is in turn mounted on the end of a motor armature shaft '55. The motor armature shaft i5 is carried by an electric motor 15. The motor 76 is mounted on a base plate H which is formed with a dovetailed surface which mates with a correspondingly shaped dovetail surface formed in a base member l8. An adjusting screw 80 is carried by a depending bearing ill formed on the under side of the base plate ll. The screw 88 is screw threaded into a threaded aperture 82 which is formed integral with the base member 18. By rotation of the screw 89, the base plate Ti and motor '16 may be moved transversely so as to cause a relative movement between the axis of the motor shaft 75 and the shaft 65 so as to tension the multiple V-belt drive '53.

The sleeve 6!, is provided to facilitate tensioning of the multiple -belt drive The bearing or journal is which supports the sleeve 69 is provided with a longitudinally extending slot through its upper wall and a binning screw 85 is provided to clamp the journal securely around the sleeve 69 to hold the sleeve in its adjusted position. To tension the V-belt 554, the binding screw 85 is loosened and the sleeve is then rotated by means of a rod or spanner wrench which is inserted in a hole (Fig. 3) formed in the sleeve 69, sufficiently to properly tension the driving belt after which the binder screw 85 is again tightened to clamp the eccentric sleeve 69 within its supporting bearing member iii.

In order to transmit a rocking motion to the work piece during rotation thereof to generate a non-circular surface on the work piece, such as an oval or elliptical shape on an automobile piston 8'3, a master cam 9% is provided. The master cam 93 is preferably keyed to a frusto-conical nose portion Si of the spindle Gil (Figs. 3 and 4) A nut or collar 92 which is screw threaded onto a threaded portion at the end of the spindle 63 serves to lock the master cam 98 in position on the conical supporting surface 9 i. This mounting for the master cam 99 is provided to facilitate changing of the master cam when it is desired to change cams for grinding different shapes on successive work pieces.

A master cam roller 95 is rotatably supported on an anti-friction bearing Si which is in turn supported by a stud S? which is journalled in a bearing surface 98 formed in the bracket 35 which is fixed relative to the swivel table 'l l. The stud 9'5 is held in fixed position relative to the bracket by means of a collar 99 which is screw threaded onto the end of the stud 9i. It will be readily apparent from the foregoing disclosure that when the master cam 99 is held in operative engagement with the periphery of the master cam roller 95 during rotation of the headstock spindle 60, a rocking motion will be transmitted to rock the rock bar 52 so as to rock the piston 81 being ground relative to the grinding wheel i5 to grind the desired oval or elliptical shape thereon.

The master cam 99 is normally held in operative engagement with the mas er cam roller 95 during a grinding operation by m ans of a yieldable device comprising a spring Hill which surrounds a stud Bill. The stud till is screw threaded into a plate it?! which is fixed relative to the swivel table -16. The spring is interposed between a threaded collar EH3 carried by the stud EB! and a washer 58 t which engages a recessed aperture M5 formed within a bracket 5% which is fixedly mounted on the rock bar 52 (Fig. 2). The spring idil is a' compression type 5 ng exerting a pressure to rock the rock bar in a clockwise direction (Fig 2) to move the master cam into operative engagement with the master cam follower roller 9. As illustrated in Fig. 2, the parts are in a loading position, in which the master cam is separated from the master cam roller by means of a mechanism to be hereinafter described during the loading operation. The compression of the spring V9 may be adjusted by turning the stud llll so that its threaded portion moves up or down relative to its threaded support I02, after which the stud IOI is clamped in adjusted position by means of a lock nut I01.

A piston such as employed in the modern automotive engine is a hollow member, one end of which is open and is usually provided with a chamfered or frusto-conical inner surface. To support the headstock end of the piston during the grinding operation, a work holding device is provided comprising a member having a frustoconical surface H0. An annular ring III having the frus'to-ccnical surface IIO formed thereon is fixedly mounted to a face plate member I I2 which has an internal cylindrical surface H3 which fits on a cylindrical portion projecting from the master cam 90. The face plate member H2 is held in a fixed position with relation to the master cam by means of screws I I4. To change the master cam 96, it is merely necessary to remove the screws II4, thereby removing the face plate member H2 and the work supporting ring III, after which the threaded collar 92 may be removed and the master cam 90 may be removed from the nosing 9i so that it may be interchanged for a new master cam of the same or different shape for succeeding grinding operations.

In'order to drive the work piece 81, a pivotally mounted yoke-shaped driving member H5 is carried by the work supporting member III. The yoke-shaped member H5 is arranged to pass within the hollow piston 81 and to straddle a pin II 6 which is inserted within the wristpin apertures of the piston 81 so that when the headstock spindle 60 is rotated by its driving motor 16, a corresponding rotary movement will be imparted to the. piston 81 to be ground. Elongated slots II4a are provided in the face plate member H2, through which the screws H4 pass, to facilitate a rotary adjustment of the plate '2 and the driving member I I5 to time the same relative to the master cam.

The other end of the piston 81 is supported by a footstock center I20 which is carried by the footstock 53. The footstock center I20 is supported in a slidably mounted sleeve I2I which is slidably keyed within a sleeve I22. The sleeve I22 is slidably keyed within an aperture I23 formed within the footstock 59. The footstock 59 is provided with a slot I24 extending its entire length and a binder screw I25 is provided by means of which the sleeve I22 may be clamped in adjusted position.

The sleeve I2I' supporting the footstock cen ter I20 is moved to and from an operative position by means of a fiuid pressure mechanism comprising a cylinder I26 having a piston I21 slidably mounted therein. When fluid is admitted either to a chamber I28 or a cylinder chamber I29, the piston I21 is caused to move either toward the right or toward the left. A yieldable connection is preferably interposed between the piston I21 and the sleeve I2I so that the footstock center I20 may be held in yieldable engagement with the piston 81 during a grinding operation. A piston rod I30 is connected at one end to the piston I21. The other end of the rod I30 is provided with a head I'3I which slides within an aperture within the sleeve I2I. When the piston I21 moves toward the right (Fig. 3), the engagement of the head I3I with the end surface of a sleeve I32 which is fixed relative to the sleeve I2I causes the sleeve I2I and the footstock center I20 to move toward the right out of engagement with the work piece 61.

A collar I33 is pinned to the piston rod I30. A compression spring [34 surrounds the piston rod I30 and is interposed between the collar I33 and the bottom of the hole in the sleeve I32 which is fixed relative to the sleeve I2I. When fluid under pressure is admitted to the cylinder chamber I29 to move the piston I21 toward the left (Fig. 3), the collar I33 exerts a pressure on the spring I34 to compress the spring I34 and move the sleeves I2I and I32 so that the rootstock center I20 moves into engagement with a center hole in the right-hand end of the piston 81 to be ground. The outer sleeve I22 may be adjusted longitudinally relative to the footstock 59 so as to adjust the compression of the spring I34 to hold the footstock center I20 in supporting engagement with the piston 81 with the desired pressure.

The footstock 59 also supports a truing apparatus by means of which the grinding wheel I5 ,may be readily trued. A diamond or other truing tool I40 is mounted in the right-hand end of a truing tool supporting rod I4I which is slidably keyed within an aperture I42 formed within the footstock 59. An adjusting screw I43 is screw threaded into the truing tool holder MI and is rotatably-supported in an end cap I44 mounted on the end of a projecting boss I45 of the footstock 59. A manually operable adjusting knob I46 mounted on the left-hand end of the adjusting screw I'43 serves to facilitate transverse adjustment of the truing tool I40 to compensate for wheel wear and also to advance the truing tool the desired amount when initially setting up the machine for a predetermined grinding operation. The diamond or truing tool I40, except for a compensating adjustment, is normally held in a fixed position with respect to the footstock 59 and rock bar 52.

The rock bar 52 is provided with a work loading fixture I50 having a V-shaped work supporting surface I5I upon which a piston 81 to be ground may be placed. The work supporting surface I5! is arranged to support the righthand end of the piston 81 (Fig. 3) until the footstock center I20 is moved into operative supporting engagement with the work piece. Movement of the center I20 into an operating position raises the piston 81 so that the piston 01 does not contact the surface I5I during the grinding operation.

It is desirable that the truing tool I40 normally be held in a fixed position with respect to the rock bar 59 and that the bar be rocked to an inoperative position for a truing operation. In the preferred construction, a mechanism is provided which is actuated by and in timed relation with the traversing movement of the table I I' for automatically rocking the bar 52 to and from an inoperative position, that is, with the work piece 31 separated from the periphery of the grinding wheel I5, and the master cam 90 separated from the follower roller before and after a-truing operation. A lever I60 is mounted on the right-hand end of a rock shaft I6 I (Fig. 5) which is journalled in agbracket I62 carried by the swivel table 44. The right-hand end of the lever I60 (Fig. 6) is provided with a yoke-shaped projection I63 which straddles a stud I64. The stud IE4 is fixedly mounted relative to an arm which is formed integral with the rock bar 52. A compression spring I66 surrounds the stud I64 and is interposed between the arm I65 and a collar I61. The yoke I63 of the arm I60 engages the collar I61 and when the lever I60 is rocked in a clockwise direction (Fig. 6), the spring I66 is compressed and the arm I65 rocked to rock the rock bar 52 to an inoperative position. The movement of the rock bar to an inoperative position is limited by means of an adjustable stop screw I68 which is carried by the arm I65.

The shaft IBI supports at its left-hand end (Fig. 5) a downwardly projecting lever. I70. A stud I'II pivotally connects the lever IIU with a toggle lever I12. A toggle lever I73 is pivotally supported by a stud I14 fixed to the swivel table 44. A stud I15 connects the toggle lever I12 and I13. The toggle lever H2 is preferably formed in the shape of a bell crank lever having a downwardly projecting arm I16 which supports a rotatable roller IT! at its lower end on a stud I18. The roller H1 is arranged in the path of a cam I19 which is fixedly mounted on the front of the machine base ID. The straight portion of the cam I19 maintains the rock bar 59 in an inoperative'position to hold'the truing tool in a fixed truing position as it is traversed across the periphery of the grinding wheel I5'to true the same.

In the full line position (Fig. 6), the toggle levers I12 and US are in a substantially straightline position and the lever Ill), shaft EBI and lever I80 are rocked in a clockwise direction to compress the spring 186 and to shift the arm I65 and the rock bar 52 to an inoperative position for a truing operation with the stop screw I68 in engagement with the swivel table 44. When'the table It is traversed toward the right, that is toward a grinding position, the piston 81 moves into position 810; in operative relation with the grinding wheel I5, andthe roller I'll rides along and down the surface of the cam I19 and assumes the position I'I'Ia. As soon as the roller I'll rides down the incline of the cam I19, the released compression of the spring I66 (Fig. 6) as well as the released compression of the spring I88 (Fig. 2) serves to rock the rock bar 52 into an operative position with the master cam 98 in operative engagement with the master cam roller 95. During this movement, the lever IE9, the lever 16, and the toggle levers I12 and H3 and the arm 1'56 move into the broken line positions Ifiila,

I'Hla, I'I2a, I'I3a and 576a. A stop screw I89 car ried by the swivel table id serves to limit the rocking movement of the lever H8 and IS!) in a counterclockwise direction (Fig. 6). When the table H is moved toward the left, the roller ill and the levers connected therewith operate automatically to rock the rock bar 52 into an inoperative position as the ground piston is moved into its truing position.

To facilitate locating the table I! with the work piec 81 in a predetermined position with relation to the grinding wheel I5, a stop device is I provided. A bracket I85 is fixedly mounted on the base Iii. The upper-end of the bracket I85 carries an adjustable stop screw 186 which is arranged in the path of a stop lug I81 which is adjustably supported on the front edge of the table II by bolts which pass within a T-slot formed therein.

Fluid under pressure for operating the footstock 53 may be supplied by any suitable means either from a central fiuidpressure system within the plant or a fluid pressure pump contained within the base I!) of the machine. Fluid under pressure passing through a pipe I9I from the source of supply enters the valve I90 and in the position illustrated in Fig. 1 passes through the pipe I92 into the cylinder chamber I29 to move the rootstock center I20 into operative supporting engagement with the work piece 81. During this movement of the rootstock center I20, fluid within the cylinder chamber I28 is exhausted through a pipe I93, through the valve I98, and out through a pipe I96. A throttle valve I95, preferably of a needle valve type, is placed in the pipe line I94 and serves to regulate the speed of movement of the footstock center I20 into operative engagement with the work piece 87.

If it is desired to grind a cylindrical surface, the rock bar 52 may be locked in a fixed position. with the master cam 90 out of engagement with the master cam roller 95. A nut I08 is screw threaded on the upper portion of the stud IOI above the arm I86 which projects from the rock bar 52, The nut 03 normally is maintained out of engagement with the arm I96. By tightening the nut I98, that is, adjusting it downward until the nut engages the arm I06 and moves it downwardly until the stop screw IE8 limits the movement of the rock bar 52, the rock bar maybe held in a fixed position for a cylindrical grinding operation.

The operation of this machine will be readily apparent from the foregoing disclosure. Assuming all of the mechanisms to have been previously adjusted, a piston 81 to be ground having a pin (I5 passing through its wristpin bore is placed in position with its open end engaging the frustoconical surface H and the yoke-shaped driver H engaging the pin H6. The outer end of the piston 87 rests upon the surface I5I of the work loading bracket I50. A control valve ISO is then actuated to admit fluid under pressure to the cylinder chamber I29, which serves to move the rootstock center I28 into operative supporting engagement with the work piece 81, thus raising the footstock end of the work piece from the work loading fixture 50. The manually operable hand wheel 2| is then rotated to traverse the table II toward the right until the stop lug I81 engages the stop screw I86 to locate the piston 81 in a predetermined grinding position with relation to the grinding wheel I5.

During the longitudinal shifting and positionposition with the master cam 98 engaging the periphery of the master cam roller 95. The headstock motor 16 and grinding wheel motor 29 having been previously set in motion by means of push button switches located on the front of the machine base, the grinding operation proceeds and the feed wheel 69 is manually rotated to feed the grinding wheel I5 toward and into the work piece 8! to grind it to the predetermined size. During this fee-cling movement of the grinding wheel IS, the rotation of the headstock spindle 60 and work piece 81 serves, through the master cam 90 and the follower roller 95, to oscillate the work piece 81 toward and from the periphery of the grinding wheel I5 so as to generate or grind a predetermined oval or elliptical contour on the periphery of the piston being ground. By providing a master cam 98 of the desired shape, any desired shape may be produced on the periphery of the piston or object being ground.

After the feeding has continued until the work has been reduced or ground to the required size, the feed wheel $0 is then rotated in a clockwise direction (Fig. 1) to move the wheel I5 out of grinding contact with the work 81. The finish ground piston 81 may then be removed from the machine and replaced with an unground' piston for the next grinding operation. If it'is desired to true the grinding wheel, the manually operable traverse wheel 29 is then rotated to shift the table I l longitudinally toward the left into a truing position, as indicated in Figs. 1 and 3. During this movement of the table H to a grinding Wheel truing position, the engagement of the roller ill with the cam W9 serves to rock the levers ll'ii, H3, H2, lit and ltt into the position illustrated in Fig. 6 automatically to rock the rock bar 52 and truing tool Mu into an inoperative fixed truing position. Continued traversing movement of the table traverses the truing tool Hill across the operative face of the grinding wheel 55 to true the same.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a piston grinding machine having a rotatable grinding wheel and a rotatable work support which are movable longitudinally and transversely relative to each other, means to traverse said work support and grinding wheel longitudinally relative to each other, means to feed said work support and grinding wheel transversely relative to each other, means to rotate said work piece, yieldable means to hold said work support in an operative position, an adjustable truing tool on said work support, means to traverse said table longitudinally to and from a truing position, and means actuated automatically when the table is traversed toward a truing position to move said work support transversely to locate the truing tool in a predetermined truing position.

2. In a piston grinding machine having a rotatable grinding wheel and a rotatable work support which are movable longitudinally and transversely relative to each other, means to traverse said work support and grinding wheel longitudinally relative to each other, means to feed said work support and grinding wheel transversely relative to each other, means to rotate said work piece, yieldable means to hold said work support in an operative position, an adjustable truing tool on said work support, means to traverse said table longitudinally to and from .a truing position, and means actuated automatically when the table is traversed toward an operative position after a truing operation to move the work support transversely into an operative position.

3. A piston grinding machine having a longitudinally traversable table, a transversely movable wheel slide, a rotatable grinding wheel supported thereon, a transversely movable rotatable work support on said table, yieldable means to hold said work support in an operative position, an adjustable truing tool on said work support, means to traverse said table longitudinally to and from a truing position, and means actuated automatically when the table, is traversed toward a truing position to move said work support transversely to locate the truing tool in a predetermined truing position.

4. In a piston grinding machine having a rotatablegrinding wheel andarotatable work support which are movable longitudinally and transversely relative to each other, means to traverse the work support and grinding wheel longitudinally relative to each other, means to feed said Work support and grinding wheel transversely relative to each other, means to rotate said work support, means to clamp a work piece thereon, a pivotal support for said work support, means including a master cam and a follower to rock said work support to cause the work to approach and recede from the grinding wheel to grind a non-circular shape on the periphery of the work piece, a truing tool adjustably supported on said pivotally mounted work support, and means actuated by the relative longitudinal movement between the grinding wheel and work support to rock said work support to an inoperative or truing position for a grinding wheel truing operation.

5. In a piston grinding machine having a longitudinally traversable table, a transversely movable slide, a rotatable grinding wheel supported thereon, a rotatable work support on said table including a rock bar, a head and footstock formed integral therewith rotatably to support a piston to be ground, a rotatable master cam and a follower to rock said bar during rotation of said headstock to generate a predetermined contour on the piston being ground, a truing tool adjustably supported on said rock bar, means to adjust the truing tool relative to the rock bar, and means including a cam and a follower actuated during the traversing movement of the table toward a truing position automatically to rock said bar to an inoperative position and to hold the truing tool in a fixed truing position during a wheel truing operation.

6. A piston grinding machine having a longitudinally movable table, a transversely movable wheel slide, a rotatable grinding wheel thereon, a work support on said slide including a pivotally mounted rock bar, a head and footstock thereon rotatably to support a piston to be ground, a

rotatable master cam and a follower to rock said bar to generate a predetermined contour on the piston being ground, a truing tool adjustably supported on said rock bar, and means including a cam and a follower which serve during a traversing movement of the table toward a truing position to rock said bar to a fixed inoperative truing position during a truing operation and automatically to shift said bar to an operative position with the master cam in engagement with the follower when the table is traversed from a truing to an operating position.

'7. In a grinding machine having a longitudinally traversable table, a transversely movable slide, a rotatable grinding wheel supported thereon, a rotatable work support on said table including a rock bar, a head and footstock on said rock bar, a headstock spindle rotatably journalled in said headstock, a master cam follower roller, a master cam removably mounted on the end of the headstock spindle adjacent to the grinding wheel, and a work supporting and driving member adjustably mounted on said master cam.

8. In a grinding machine as claimed in claim 1, the combination with the parts and features therein specified, of a stop to locate said bar in an inoperative or truing position, yieldable means normally to maintain said bar in an Operative position with the master cam in operative engagement with the follower, means including a toggle lever mechanism on said table to rock said bar to an inoperative position, and means includingacarn on saidbase to actuate said. toggle lever mechanism When the table is traversed longitudinally toward a truing position to rock said bar to an inoperative position and to hold it in an inoperative or truing position during a grinding wheel truing operation.

9. In a grinding machine as claimed in claim 1, the combination with the parts and features therein specified, of a stop to locate said bar in 10 an inoperative 01 truing position, yieldable means normally to maintain said bar in an operative position, means including a toggle lever mechanism to rock said bar to an inoperative position, and means including a cam which is arranged to actuate said toggle lever mechanism when the table is traversed longitudinally toward a truing position to rock said rock bar into an inoperative position and to hold it in said position during a grinding wheel truing operation.

HERBERT A. SILVEN. 

